1. Field of the Invention
The present invention relates to a recording medium provided with a porous ink-receiving layer laminated on the substrate and a method for conducting a record thereon by an ink-jet system.
The ink-jet recording system is a system of ejecting minute ink droplets by various operating principles and depositing them to a recording medium such as paper to make a record of images, characters or the like, has features that high speed, low-noise and multi-color recording can be easily realized and a compatibility in recording pattern is high without need for development or fixation, and then has rapidly been spreading in various uses. Furthermore, according to the multi-color ink-jet recording system, there can be formed multi-color images, which are almost equal in quality as compared with a color print according to the color photography process or a multi-color print according to the plate making process, and recorded articles can be obtained at lower cost than those by a usual multi-color printing or print in case of a small number of copies, and therefore the multi-color ink-jet recording system is being widely applied to the field of full-color image recording.
2. Related Background Art
With the request for improvement in recording characteristics, such as speedier, more precise and fully-colored records, an ink-jet recorder and recording method have so far been improved, but at the same time high level characteristics have been required for a recording medium to be used.
According to the ink-jet recording system, an ink comprising a large amount of a solvent such as water or a mixture of water and an organic solvent is used from the need for ejecting ink droplets from a nozzle toward a recording medium at high speed. Thus, to obtain an recorded image having a high color density, a large amount of ink must be used. Besides, since ink droplets are continuously ejected, there may occur a beading phenomenon in which ink dots are joined, causing disorder in an image. To prevent this beading phenomenon, a large amount and a high speed of ink absorption in a recording medium is required.
Such being the case, many types of recording media with a porous layer comprising inorganic particles such as alumina hydrate formed on the substrate as described in Japanese Patent Application Laid-Open No. 2-276670 have been proposed to improve the absorbency, coloration and resolution. Furthermore, a recording medium with an ink fixing layer comprising a transparent resin soluble or swellable in the solvent of an ink formed on the substrate as described in Japanese Patent Application Laid-Open No. 4-101880 has been proposed.
Furthermore, to improve an ink-absorbency, there has been proposed a recording medium with two upper and lower porous particle layers having different pore radii and comprising porous inorganic particles and binder as described in Japanese Patent Application Laid-Open No. 62-111782.
Besides, a recording medium with a porous polymer layer (mixture layer of organic particles and inorganic particles) formed on a porous alumina layer by applying and drying a dispersion comprising a polymer latex having an average particle diameter of from 0.05 to 0.5 xcexcm and inorganic particulates such as silica particles has been also proposed as described in Japanese Patent Application Laid-Open No. 7-237348.
On the other hand, to improve a resolution while retaining an ink-absorbency, a recording medium having two peaks in a pore radius distribution curve has been also proposed as described in Japanese Patent Publication No. 63-22997.
Also, with the ink-jet recording system, there has often been used an ink of such a type as dissolving the dye component into a solvent thus far. However, since the dyestuff ink is poor in light fastness and ozone-resistance by nature, a long-term storage of recorded documents has brought about a problem of fading or discoloring. Thus, there has been proposed a method in which recording is conducted on a recording medium provided with a porous layer comprising a thermoplastic resin material on the substrate and then a porous layer is fused under an action of heat or pressure to make the recording medium denser, as described in Japanese Patent Application Laid-Open No. 58-136482 and U.S. Pat. No. 5,374,475. Still more, there has been also proposed a recording medium provided with a two-layered ink-receiving layer in which an inorganic pigment layer having a large ink-absorptivity is provided on the substrate and a top surface layer comprising a thermoplastic organic polymer is provided, as described in Japanese Patent Publication No. 2-31673.
However, these background arts have the following problems.
In a recording medium with porous layer comprising inorganic particles as described in Japanese Patent Application Laid-Open No. 2-276670, neither sufficient light fastness nor ozone-resistance is obtained when using a dyestuff ink.
Besides, a recording medium with an ink fixing layer using a resin soluble or swellable in an ink solvent as described in Japanese Patent Application Laid-Open No. 4-101880 has a problem of being slow in drying of ink and sticky for a while after the completion of recording.
Also, with a recording medium with a two-layered ink-receiving layer as described in Japanese Patent Application Laid-Open No. 62-111782, an ink-absorbency can be improved, but defects in the adjustment of coating conditions and drying conditions for obtaining the uniformity of a coated film or the reduction in fault of a coated film occur in the step of forming the two layers, causing not a few problems in production.
Further, according to a recording medium with a porous polymer layer formed as a upper layer of a two-layer construction by using a polymer latex and inorganic particulates as described in Japanese Patent Application Laid-Open No. 7-237348, an ink-absorbency can be further promoted, but the two layer construction also makes it difficult to obtain a uniform coated film. Particularly, defects such as cracks or fissures may occur. Furthermore, when using a large amount of ink, no sufficient examination has been made on what porous construction the porous polymer layer should be composed of.
Still also, in a recording medium having two peaks in a pore radius distribution curve as described in Japanese Patent Publication No. 63-22997, the pore radius distribution curve has two peaks due to pores by voids formed between the aggregates of primary particles of 0.2 xcexcm or below in diameter and due to pores in the particles themselves. Here, the pores are so set as to increase the pore volume having small radii of 0.05 xcexcm or below. In case of using a photo ink rich in solvent and surfactant to promote the gradation in a half tone or the like under recent circumstances of requiring a photographic tone, no sufficient absorbency is always obtained with a pore structure as mentioned above. Namely, an ink-absorbency due to voids having a larger peak pore radius becomes further needed, but in the formation of a pore, formed between the aggregates of very small primary particles, it is difficult to form a greater amount of pores having a sufficiently large peak radius. Accordingly, when a higher speed printing than achieved by a conventional printing method is required, or for a decrease in the number of printing passes, no sufficient absorbing power for ink has been obtained.
And, according to a method in which recording is conducted on a recording medium provided with a porous layer comprising a thermoplastic resin material and then the porous layer is fused to make the recording medium denser, as described in Japanese Patent Application Laid-Open No. 58-136482 and U.S. Pat. No. 5,374,475, problems of fading or the like of dyestuff ink can be solved, but when the formation of a denser record image is needed, the ink-absorbency remains yet insufficient.
And also, in a two-layered recording medium as described in Japanese Patent Publication No. 2-31673, problems on production remain as with the above two-layered recording medium.
The present invention has been accomplished in consideration of the problems of the individual background art described above.
An object of the present invention is to provide a recording medium which causes neither bleeding nor flood, which is high in an absorbing power and which is capable of obtaining an excellent gradation, even when using an ink-jet printer with a great amount of ink supplied and using a diluted ink overlappingly plural times of recording or using a diluted ink and a thick ink in combination for acquiring a higher gradation, and further which can exhibit a sufficient absorbing power also in a high-speed printing for a decrease in the number of printing passes, and also which does not necessary to select the type of a substrate, is easy in production, is preventable in the fading of a record image, and is capable of widely coping with using environments, taking the water-fastness into consideration.
An another object of the present invention is to provide a recording method capable of performing good recording to the recording medium.
The above objects can be achieved by the present invention described below.
According to the present invention there is provided a recording medium provided with a porous ink-receiving layer containing thermoplastic resin particles and inorganic pigments laminated on the substrate, wherein the pore radius distribution curve of the above porous ink-receiving layer has a maximum peak in a pore radius range of from 1 xcexcm to 10 xcexcm and at least one peak in a pore radius range of from 0.001 xcexcm to 0.1 xcexcm and the total volume of pores having pore radii of from 0.1 xcexcm to 20 xcexcm is not less than 0.5 cm3/g.
According to the present invention there is also provided a recording method for depositing an ink to the porous ink-receiver layer of the recording medium by the ink-jet system.